1. Field of the Invention
The subject invention relates generally to a driveline system for a vehicle transmission. More particularly, the present invention relates to a universal joint component of the driveline system subject to high torsional loads and a method of forming the same by stamping.
2. Description of the Prior Art
A drive axle assembly of an automotive vehicle transmits torque from an engine and a transmission to drive vehicle wheels. The drive axle assembly changes the direction of the power flow, multiplies torque, and allows different speeds between the two of the drive wheels. The drive axle assembly includes a plurality of components engaged in operative communication one with the other. One of these components is a universal joint, subject to high torsional loads, typically greater than 2,000 ft. lbs. applied at the joint. Typically, the universal joint includes a pair of bifurcated yokes or yoke portions, which are secured to drive shafts and which are interconnected by a cruciform for rotation about independent axes. The cruciform includes four orthogonal trunnions with each opposing pair of axially aligned trunnions mounted in a pair of aligned bores formed in the bifurcated yokes.
Typically, a bearing cup is secured in each bore and a bearing assembly is retained in the bearing cup such that each yoke is supported for pivotal movement relative to a pair of the trunnions. Various conventional universal joints having yoke portions are known to those skilled in the vehicle driveline art and are widely used in the automotive industry today. These universal joints are disclosed in U.S. Pat. Nos. 4,307,833 to Barnard; 5,601,377 to Ohya; 5,622,085 to Kostrzewa; 5,845,394 to Abe et al.; 6,162,126 to Barrett et al.; 6,280,335 to Wehner et al.; 6,336,868 to Kurecka et al.; 6,408,708 to Sahr; 6,591,706 to Harer et al.; and 6,736,021 to Adams et al.
The U.S. Pat. No. 5,601,377 to Ohya, for example, teaches an automobile steering column that transmits the rotation of the steering wheel to the steering gearbox. For increasing the degree of freedom of geometric arrangement of the steering system, the steering column has a plurality of steering shafts which are connected with each other by universal joints. The universal joint, taught by the U.S. Pat. No. 5,601,377 to Ohya, has a pair of conventional yokes and a cross member. Each yoke has a base portion and a pair of arm portions or lugs opposed to each other in a diametral direction of the yoke and extend in an axial direction of the yoke. Each arm portion has a circular opening and sides extending in a parallel relationship with the axial direction of the yoke. The yoke of the U.S. Pat. No. 5,601,377 to Ohya is taught to be connected to a steering shaft and is not subjected to numerous rotational movements as, for example, a yoke portion connected to a universal joint of a driveline and is, therefore, not considered as being feasible for use on the driveline. In addition, the yoke does not include reinforcing features of any kind to prevent bending of the arm portions during rotation of the yoke.
The U.S. Pat. No. 5,845,394 to Abe et al., for example, teaches a method of manufacturing a yoke portion having two spaced lugs for a universal joint from a blank of a sheet metal to receive the yoke portion of a uniform thickness. Similar to the yoke taught by the aforementioned U.S. Pat. No. 5,601,377 to Ohya, the spaced lugs are not reinforced to provide structural integrity of the yoke portion. Again, the yoke portion is taught to be connected to a steering shaft and is not subjected to numerous rotational movements as, for example, a yoke portion connected to a universal joint of a driveline and is, therefore, not considered as being feasible for use on the driveline.
To reduce the effect of vibration and the resulting noises, manufacturers have used various methods to construct drive shafts and universal joints connected thereto. Typical prior art yoke portions are iron cast to provide durability but are difficult to balance.
The prior art has also proposed making yokes for a universal joint of an automotive driveline system by bolting a U-shaped yoke member to a plurality of plates, one of which includes a shaft, such as disclosed, for example, in U.S. Pat. No. 4,702,722 of Narue et al. As will be understood by those skilled in this art, however, any misalignment of these several components of this yoke assembly will result in vibration or the components may become misaligned following assembly. Further, this yoke assembly is relatively expensive, particularly when compared with the improved universal joint of this invention.
The prior art also includes forks for yoke assemblies for cardan or constant velocity joints. U.S. Pat. No. 4,995,849 discloses a cardan joints for a steering column which is produced by stamping from a metal sheet. However, the disclosed fork would not be suitable for the universal joint of an automotive driveline assembly subject to high torsional loads.
The opportunity exists for an improved universal joint and method of manufacturing the same that will reduce the mass of the yoke portion thereby reducing the effect of vibrations and the resulting noises, add structural integrity to the universal joint, make it easier to balance, and increase performance of drive line applications at a low cost and a high volume.